The present invention relates to derivatives of substituted cephalosporanic acid and antibiotics comprising the derivatives of cephalosporanic acid. More in detail, the present invention relates to the derivatives of substituted cephalosporanic acid, represented by the formula (I): ##STR2## wherein R.sup.1 represents a 4-pyridylthiomethyl group ##STR3## an alpha-aminobenzyl group ##STR4## a cyanomethyl group (N.tbd.C--CH.sub.2 --) or a 1-tetrazolylmethyl group ##STR5## R.sup.2 represents a hydrogen atom, an acetoxy group or a (5-methyl-1,3,4-thiadiazol-2-yl)thio group ##STR6## R.sup.3 represents a hydrogen atom, a hydroxyl group, a carbamoyl group, an alkyl group having 1 to 4 carbon atoms or --(CONH).sub.m (CH.sub.2).sub.n --COOH wherein m is 0 or 1; n is 0, 1 or 2 and the carboxyl group may have been converted to a salt or an ester thereof; p is 0, 1 or 2 and X represents carbon atom or nitrogen atom and the antibiotics comprising the derivatives of substituted cephalosporanic acid, represented by the formula (I).
The derivatives of substituted cephalosporanic acid according to the present invention (hereinafter referred to the present compounds) are the novel antibiotics of quite a new type in the sense that each of the present compounds has been obtained by chemically modifying a conventional antibiotic comprising a substituted cephalosporanic acid, and although the antibiotic property of the parent compound has been lost by the chemical modification, the once-lost antibiotic property is exhibited by the present compound after it is absorbed into living body of the host to which the present compound has been administered.
Antibiotics comprising substituted cephalosporanic acid, so-called, cephalosporins, are now broadly used because of their favorable antibiotic property and of their fairly high selective activity against noxious bacterial species, however, because of their activity also against useful bacterial species habitually present in living body of the host to which the antibiotic is to be administered, such an antibiotic has a serious demerit of disturbing the useful intestinal bacterial colonies when it is orally administered to the host resulting in causing colitis or diarrhea on the host in some cases.
The present inventors have found, after studying for obtaining antibiotics which do not have such a demerit and still exhibit the antibiotic activity against noxious bacteria, that the derivatives of substituted cephalosporanic acid, represented by the formula (I) are quite suitable for the object of the present inventors, and they have attained the present invention.
Accordingly, the object of the present invention is to provide the derivatives of substituted cephalosporanic acid, which never disturb the intestinal bacterial colonies while exhibiting an excellent antibiotic activity against noxious bacteria.